There is used an external medicine which exerts a systemic action (a systematically acting external medicine) by entering a drug absorbed through the skin or the like into systemic circulation, or alternatively an external medicine which exerts a medicinal effect topically (a topically acting external medicine) with a drug absorbed through skin or the like. Furthermore, a cosmetic whose active ingredient is intended to be absorbed percutaneously (a percutaneous absorption cosmetic) is also used. A main technical problem in the above preparations is how to allow an active ingredient to be absorbed efficiently into the body.
A core-shell structured particle, which has a structure of covering a core portion containing an active ingredient with a shell portion containing a surfactant, is proposed as a preparation which allows an active ingredient to penetrate percutaneously (Patent Documents 1 and 2).